Sprocket-wheel.



Ni'rnn STATES PATENT QFFICE.

NEEE E. PARISH, or. oLEvELAND, OHIO, ASSIGNOR TO THE PARISH & BINGHAMCOMPANY, OF SAME PLAoE.

SPROCKET-WHEEL.

SPECIFICATION forming part of Letters Patent No. 637,654, dated November21, 1899.

Application filed October 13, 1898. Serial No. 693,395. (No model.)

To CLZZ whom it may concern.-

Be it known that I, NEFF E. PARISH, a citizen of the United States, anda resident of Cleveland, county of Guyahoga, and State of Ohio, haveinvented a new and useful Improvement in Sprocket-Wheels, of which thefollowing is a specification, the principle of the invention beingherein explained and the best mode in which I have contemplated applyingthat principle, so as to distinguish it from other inventions.

My improved bicycle sprocket-wheel, formed by cold-pressing the metal,possesses many advantages over sprocket-wheels made by the old forgingprocessby giving a much denser product, the difference being especiallyincreased at the surface, where hardness is most desired, and by givinga clean uniform surface free from scale and imperfections. This is ofconsiderable importance in the subsequent treatment of the sprocketbefore nickeling and causes a considerable saving in the cost of suchtreatment. Before the steel can be electroplated all of this scale mustbe removed and a chemically-clean bright surface prepared. Where thesprocket-wheels have been made by the cold-pressing process, thissurface is clean, dense, and with few or no imperfections, and hence thecost of preparation for electroplating is much less than with those madeby the usual process of hotforging. The process of cold-pressing efiectsan important and advantageous diiference in the chemical nature of theproduct made in this way over that made by hot-forging. When steel isheated for hot-forging, the surface always burns to a greater or lessdegree, depending upon the length of time of heating, upon thetemperature used, and upon the number of times it must be heated foreach step in the process of shaping. This burning at the surfaceconsists in a chemical union of the iron and carbon of the steel withthe oxygen of the air, whereby the carbon passes off iron, or what thepractical forger calls taking the life out of the metal. Inconsequenceof this chemical action many defective sprocket-wheels arealways produced by the method of hot-forging, and often the defectcannot be located until the wheel is used, thus causing serious loss tothe makers of hicycles When such wheels must be replaced. In mycold-pressed sprockets, the surface of the metal is not oxidized in theleast and thus is not injured in any way. No scale is formed, and nopart of the carbon is removed. In the cold-pressingof sprocket-wheelsthere is not only no removal of carbon from the surface of the metal,but an advantageous chemical change takes place, whereby the surface ismade harder. Carbon exists in steel in several different methods ofchemical union. One such combination of carbon, causing the hardness ofthe steel to increase, is known as hardening-carbon and gives to steelthe well-known effect of quenching or hardening. The cold-pressing ofsprocket-wheels causes the carbon near the surface of the metal tochange to this hardening condition, producing the efiect of surfacehardening and at the same time leaving the interior metal tough.Cold-pressing also increases the rigidity and stiffness of the metal andraises its elastic limit. Allof these advantageous effects produced incold -pressing over hot-forging sprocket-wheels are intensified in thethinner part or web, because this part being-small and thin is moreliable to burn through and to become fatally weak by the reheatingnecessary for hot-forging, while in cold-pressing this part has the mostof the hardening-carbon and is hence strongest at these weaker points.

The annexed drawings and the following description set forth in detailone mode of carrying out the invention, such disclosed mode constitutingbut one of various ways in which the principle of the invention may beused.

Referring -to the drawings, Figure I is a plan view of a steelsprocket-blank before compression. Fig. II is a central sectional Viewof the web-compression dies. Fig. III is a central sectional view of thesprocket-blank after being operated upon by said dies. Fig. IV is acentral sectional view of the rim-compressing dies. Fig. Vis a centralsectional View through the sprocket-blank after it has been operatedupon by the rim-compressing dies.

In producing myimproved steel sprocket, a blank A of any suitable designis placed Without heating between two compressing-dies, as BC, and theweb portion a of the sprocket is compressed to a greatly-reducedthickness between the projecting portions 1) 0, respec tively, of saiddies, thereby greatly increasing the hardening-carbon in said webportion. The teeth of the sprocket-blank are then punched out in anysuitable manner, and the blank is then placed between the two diesD E,having the curved rim-compressing sur faces 01 6, whereby the teeth arerounded off form, asshown in the drawings. It will thus be seen that asteel sprocket-wheel is formed which has the opposite side faces of itsteeth surface-hardened and the metal of the peripheral faces or edges ofthe teeth less hard than the metal forming said side faces.

Other modes of applying the principle of my invention may be employedinstead of the one explained. l

I therefore particularly point out and distinctly claim as myinvention 1. A steel sprocket-wheel, having its teeth surface-hardened,the interior of said teeth being of tough metal and having the carbon inthe web portion mainly'in the hardening condition, substantially as setforth.

2. A steel sprocket-wheel having the opposite side faces of its teethsurface-hardened and having the metal of the peripheral faces of theteeth less hard than said side faces, substantially asset forth.

Signedby me this 23d day of September, 1898. xii,

I NEFF E. PARISH.

Attest: V

D. T. DAVIES, J. O; TURNER.

